JP7637389B2 - Intramedullary nail - Google Patents

Description

Applicable under Article 30, Paragraph 2 of the Patent Act. Products will go on sale to hospitals (mainly orthopedics) across Japan from November 16, 2020.

Application of Article 30, Paragraph 2 of the Patent Act: Sales activities to promote the product will begin on November 16, 2020 using product brochures, samples, procedure manuals, and explanatory materials.

Article 30, Paragraph 2 of the Patent Act applies. A print advertisement for the product was placed in the "Kurume University School of Medicine Orthopaedic Surgery Alumni Association Journal: Orthopaedic Surgery Department 2020 No. 27" published by the Department of Orthopaedic Surgery, School of Medicine, Kurume University, on December 12, 2020. A print advertisement for the product was placed in the "Orthopaedic Surgery and Trauma Surgery 141st Western Japan Orthopaedic and Trauma Surgery Society Academic Conference Abstracts Vol. 70" published by the Department of Orthopaedic Surgery, School of Medicine, Kurume University, on May 13, 2021 (academic secretariat).

The present invention relates to an intramedullary nail. More specifically, it relates to an intramedullary nail that can prevent problems during the surgical procedure for fractures on the proximal side of the femur, and can be placed in an ideal position within the femur to connect and firmly fix bone fragments.

Traditionally, in fracture treatment requiring surgery, bone set devices have been used that combine an intramedullary nail, which is inserted along the longitudinal axis of the bone to be treated, with a lag screw that has a male thread formed around the shaft, and are used particularly in bone set procedures for fractures on the proximal side of the femur.

Many different types of intramedullary nails are already known for use in such bone fixation procedures. For example, an intramedullary nail that is driven into the femur from the proximal end has been proposed to repair femoral trochanteric fractures, femoral subtrochanteric fractures, femoral intertrochanteric fractures, or femoral neck base fractures (see, for example, Patent Document 1).

In addition, in a procedure using an intramedullary nail that is driven into the femur from the proximal end, a hole is drilled in the femur from the proximal side to the distal side with a reamer, and the intramedullary nail is inserted into the hole.

In addition, a lag screw is inserted through a screw hole formed in the proximal part of the intramedullary nail, and its tip is positioned near the center of the femoral head.

The inserted lag screw is pressed and fixed via a set screw attached to the top of the intramedullary nail. In this way, the bone fragments at the fractured site can be connected and firmly fixed via the intramedullary nail and lag screw. Also, by positioning the tip of the lag screw within the femoral head, it is possible to apply appropriate pressure to the fractured site and promote bone union.

In addition, for conventional intramedullary nails, a structure has been proposed in which the direction of the screw hole through which the lag screw is inserted is set according to the anteversion angle, which is the angle at which the neck of the femur is tilted forward, in order to improve compatibility with the femur.

Here, the "anteversion angle" is the angle θ between the femoral neck axis S1, which is the axis connecting the center of the head F1 of the femur F and the center of the neck F2 (the position at the same distance from the outer edge), and the femoral condyle axis S2, which is the axis connecting the two condyles (posterior condyles) of the medial condyle F3 and the lateral condyle F4 at the distal part of the femur F, as shown in Figure 1(a).

Figure 1(a) shows the right femur viewed from the proximal side to the distal side, showing the structure of the femoral head and its surrounding area. Also, the symbol H in Figure 1(a) indicates the hip joint.

Although this anteversion angle varies from person to person, it generally results in a shape in which the neck of the femur is tilted forward (tilted to the upper left as seen in Figure 1(a)), i.e., the femoral neck axis S1 opens forward relative to the femoral condyle axis S2. Note that for some people, the neck of the femur may be tilted backward (retroversion angle).

Because this anteversion angle causes the femoral head to be tilted forward, conventional intramedullary nails have screw holes formed in the direction that takes the anteversion angle into consideration.

Special table 2017-535401

Here, the following problems occur with conventional bone sintering procedures using intramedullary nails, including intramedullary nails in which screw holes are formed taking into account the inclination of the anteversion angle.

First, as a premise, when viewed from the side, the shape of the femur is such that, as shown in FIG. 2(a), the diaphysis F5 located between the proximal and distal femur has a forward curved shape (symbol C1, hereafter referred to as the "lordotic shape") with the apex P of the curve on the forward side.

Here, Fig. 2(a) shows the shape of the right femur in a composition (side view) in which the right femur is viewed from the inside to the outside of the human body along the coronal plane of the human body. Also, Fig. 2(b) shows the shape of the right femur in a composition (front view) in which the right femur is viewed from the front to the rear of the human body along the sagittal plane of the human body.

In addition, FIG. 1(b) illustrates the coronal plane K1, sagittal plane K2, and transverse plane K3, which are planes that cross the human body. Here, the coronal plane K1 is a plane that divides the body into front and back. The sagittal plane K2 is a plane that passes through the body from front to back and divides it into left and right, or a plane parallel to this. The transverse plane K3 is a plane that divides the body into top and bottom. In this specification, when specifying a direction, the terms coronal plane, sagittal plane, and transverse plane, or the direction along these planes may be used as necessary.

Figures 2(a) and 2(b) also show the medullary cavity center M that extends along the longitudinal direction inside the femur, the positions M1 of both ends of the medullary cavity center, and the position M2 of the medullary cavity center that corresponds to the apex P of the lordotic shape (the position of the medullary cavity center that is the apex of the curve).

In general, this lordotic shape is a curved shape of the femur in the range from a position just below the lesser trochanter (position indicated by reference character L1 in FIG. 2(b)) to a position just above the patella Q (position indicated by reference character L2 in FIG. 2(b)) (see FIG. 2(b)). In this specification, the "lordotic shape" of the femur does not refer to the curvature of the entire length of the femur, but rather refers to the curvature in the range from the position just below the lesser trochanter to a position just above the patella Q, which is the range that should be secured by the intramedullary nail.

As shown in FIG. 3, in the femur, when viewed from the proximal to the distal side along the longitudinal direction of the femur and from the front when the posterior condyle is located downward (hereinafter, the viewpoint viewed from the same direction will be referred to as the "front view"), the direction of curvature in the above-mentioned lordotic shape is inclined with respect to reference line B, which is a line that is approximately perpendicular to reference line A connecting the posterior condyles (medial condyle F3 and lateral condyle F4) and passes through position M1 at both ends of the center of the medullary cavity (indicated by symbol C2 in FIG. 3, the lateral curve shape described below).

More specifically, in a frontal view of Figure 3, the inclination of the direction of curvature in the lordotic shape relative to the reference line B is represented by the angle θ between the reference line C connecting the positions M1 of both ends of the center of the medullary cavity and the position M2 of the center of the medullary cavity corresponding to the apex P of the lordotic shape, and the reference line B.

The reference line A shown in FIG. 3 is a line located on the reference plane X, which is a plane on which the posterior condyles of the femur (medial condyle F3 and lateral condyle F4) and the posterior edge F6 of the greater trochanter of the femur (posterior side of the greater trochanter) are located in the same plane, as shown in FIG. 4(a). The reference line A is also a line that corresponds to the femoral condyle axis S2 described above. The femur shown in FIG. 3 is a left femur.

Figure 4(b) shows the position of the posterior condyles (medial condyle F3 and lateral condyle F4) and the position of the posterior edge F6 of the greater trochanter of the femur when the left femur is viewed from the outside to the inside of the human body along the coronal plane of the human body, and Figure 4(c) shows the position of the posterior condyles (medial condyle F3 and lateral condyle F4) when the left femur is viewed from the distal side to the proximal side along the longitudinal direction of the human body.

In general, when viewed from the front as shown in Figure 3, the shape of the femur often has a lordotic shape in which the direction of curvature does not coincide with reference line B. In other words, the direction of curvature in the lordotic shape is not located in a direction approximately perpendicular to reference line A (the 12 o'clock direction in Figure 3), and the shape is tilted either outward or inward when viewed from reference line B (a shape tilted in the clockwise or counterclockwise direction in Figure 3).

When viewed from the front, the direction of curvature of the lordotic shape relative to the reference line B is inclined outward as shown in Figure 3 (a shape inclined counterclockwise in Figure 3), and this is called an "external curvature shape."

Also, unlike Figure 3, when viewed from the front, the direction of curvature in the lordotic shape relative to the reference line B is tilted inward when viewed from the reference line B (a shape tilted in a clockwise direction in Figure 3) and is called an "internal curvature shape." Note that "internal" here means the direction along the coronal plane of the human body.

In addition, FIG. 5 shows an example of an internal curve shape, with a reference plane X on which the posterior condyles (medial condyle F3 and lateral condyle F4) of the right femur and the posterior edge F6 of the greater trochanter of the femur are located on the same plane, and an inclined plane Y showing the direction of curvature in the lordotic shape tilted inward when viewed from the reference line B.

As shown in FIG. 5, the inclined surface Y is inclined with respect to the reference surface X, and the direction of curvature in the lordotic shape is inclined at an angle.

As such, the shape of the femur is often characterized by an outward curve or an inward curve, depending on the inclination of the direction of the lordotic curve relative to the reference line B.

As described above, the shape of the femur has a lordotic shape when viewed from the side. Also, when viewed from the front, the shape is often an outward curve due to the inclination of the direction of curvature in the lordotic shape relative to the reference line B, and depending on the person, it may also have an inward curve (hereinafter referred to simply as an "outward curve" and an "inward curve").

Given the shape of the femur, previous intramedullary nails were not designed to accommodate the external or internal curvature of the femur.

That is, a conventional intramedullary nail 300 in which a screw hole is formed taking into account the inclination of the anteversion angle has a shape such as that shown in Figures 6(a) to 6(e).

Figures 6(a) and 6(b) show the shape of the intramedullary nail 300 as viewed from the front (as viewed from the front to the rear when inserted into the femur). Reference numeral 300a denotes the shaft. Figure 6(b) also shows a lag screw 301 and a locking screw 302 that are used in combination with the intramedullary nail 300.

Figure 6(c) shows the shape of the intramedullary nail 300 when viewed from the side (when inserted into the femur, viewed from the inside to the outside along the coronal plane of the human body). Figure 6(d) shows the shape of the intramedullary nail 300 when viewed from the front (when inserted into the femur, viewed from the proximal side to the distal side), and Figure 6(e) shows an image of the intramedullary nail 300 inserted straight into the longitudinal direction of the femur (viewed from the front).

As shown in Figures 6(a) and 6(b), the shaft 300a of this intramedullary nail 300 extends straight in the vertical direction in the figure.

As shown in FIG. 6(c), when the intramedullary nail 300 is viewed from the side, the shaft 300a has a curved portion. This curved portion is shaped to adapt the shape of the shaft 300a of the intramedullary nail 300 to the lordotic shape of the femur described above, and when inserted into the femur, it becomes a portion that curves from the front to the back along the sagittal plane of the human body.

As shown in FIG. 6(d), when viewed from the front, the intramedullary nail 300 has a screw hole for inserting the lag screw 301 at an angle indicated by the symbol θ1, taking into account the inclination of the anteversion angle.

The intramedullary nail 300 has a curved portion formed in the shaft 300a in accordance with the lordotic shape of the femur, and the direction of curvature of this curved portion is perpendicular (the line marked with the symbol Y1) to the reference line A connecting the posterior condyles (the medial condyle F3 and the lateral condyle F4) when viewed from the front, as shown in FIG. 6(e).

In other words, when the intramedullary nail 300 is inserted straight into the longitudinal direction of a femur having an external curve (when the longitudinal direction of the femur is aligned with the longitudinal direction of the shaft 300a), the external curve shape C2 of the femur, i.e., the reference line C, and the direction of the bend of the curved portion of the shaft 300a (line indicated by symbol Y1) do not coincide with each other (see FIG. 6(e)).

In reality, as described below, if the intramedullary nail 300 is inserted straight into a femur having an external curvature, the femoral cortical bone and the intramedullary nail 300 may come into contact during insertion, making it difficult to insert the nail further distally. For this reason, FIG. 6(e) is an image showing the positional relationship assuming that the intramedullary nail 300 has been inserted to a predetermined position (optimum depth) on the distal side.

In this way, the direction of curvature of the curved portion of the shaft 300a of the intramedullary nail 300 is different from the direction of curvature of the femur in its lateral curvature shape.

Therefore, when using the intramedullary nail 300 to treat a femur with an externally curved shape, if the tip of the intramedullary nail 300 is inserted from the proximal side to the distal side of the femur (the direction indicated by symbol D in FIG. 7(a)), the tip of the intramedullary nail 300 will come into contact with the cortical bone of the femur midway through the shaft, making insertion difficult, due to the difference in the direction of the curve in the externally curved shape of the femur and the direction of the curve in the curved part of the shaft 300a (see FIG. 7(a)).

Then, in order to avoid a state in which it becomes difficult to further insert the intramedullary nail 300, the intramedullary nail 300 is externally rotated (rotated outward with respect to the femur) together with the target device (not shown) supporting the intramedullary nail 300 (rotated in the direction indicated by symbol R1 in FIG. 7(b)) so that the tip of the intramedullary nail 300 does not come into contact with the cortical bone of the femur, and is inserted further distally (in the direction indicated by symbol D in FIG. 7(b)).

The right diagram of Figure 7(a) and the right diagram of Figure 7(b) are schematic enlarged views showing the positional relationship between the tip of the intramedullary nail 300 and the cortical bone inside the femur.

Here, when the intramedullary nail 300 is externally rotated and inserted into the distal side of the femur, the external rotation of the intramedullary nail 300 also rotates the direction of the screw hole into which the lag screw 301 is inserted. That is, the direction of the screw hole, which was originally formed at the angle indicated by the symbol θ1 (see Figures 6(d) and 6(e)) taking into account the inclination of the anteversion angle, is tilted further forward.

As a result, when the lag screw 301 is inserted into the rotated screw hole, the tip of the lag screw 301 is positioned forward of the center of the femoral head F1, as shown in FIG. 8(a). Note that in FIG. 8(a), the arrow marked with the symbol f indicates the direction toward the forward side.

In other words, in order to prevent inversion or rotation of the femoral head after surgery using the lag screw 301, it is preferable to position the tip of the lag screw 301 so that it is located near the center of the femoral head F1. However, by externally rotating the intramedullary nail 300, the tip position of the lag screw 301 shifts forward from the desired position near the center of the femoral head F1. In other words, there was a risk that the intramedullary nail 300 would result in an inappropriate installation position of the lag screw 301.

In addition, in response to such a shift in the position of the tip of the lag screw 301, which is located forward of the center of the femoral head F1, the femur is compressed from the outside (in the direction indicated by symbol P1 in FIG. 8(b)) to reset the position of the tip of the lag screw 301 to be near the center of the femoral head F1. This compression forcibly shifts the position of the femoral head F1 forward.

When the femur was compressed from the outside to forcibly shift the femoral head F1 forward, a gap was created between the bone fragments to be fixed (see the part indicated by the symbol P2 in Figure 8(b)).

In addition, by applying pressure and shifting the femoral head forward, the shaft of the bone moves back and forth in an attempt to return to its original shape, causing the knee to internally rotate (turn inwards), which can affect walking and lead to a condition known as hyper-anteversion.

In addition, the intramedullary nail 300 has screw holes formed at a fixed angle in the direction of the screw hole formation in accordance with the angle of the anteversion angle, so this preset fixed angle is changed by pressure, and this change in angle can also cause a decrease in the user's walking ability. Note that Figures 8(a) and 8(b) show the right femur.

As described above, when conventional intramedullary nails were used on femoral bones with an external curvature, problems arose during insertion, and the intramedullary nail or lag screw could not be placed in an ideal position within the femur, making it impossible to adequately fix bone fragments and promote bone union in fractures on the proximal side of the femur.

The present invention was devised in light of the above points, and aims to provide an intramedullary nail that can prevent problems that occur during the surgical process for fractures on the proximal side of the femur, and can be placed in an ideal position within the femur to connect and firmly fix bone fragments.

In order to achieve the above object, the intramedullary nail of the present invention is used when the proximal side of the femur is fractured by inserting it into the femur from the proximal side to reposition and fix each bone fragment, and has a cylindrical body with a through hole formed therein, constituting one end side of the body, a proximal body part with a screw hole intersecting the through hole formed therein, a shaft part connected to the proximal body part, constituting the intermediate part of the body, having an outer circumferential diameter smaller than but equal to the outer circumferential diameter of the proximal body part, and extending toward the other end side of the body, and a distal body part connected to the shaft part and constituting the other end side of the body, wherein the shaft part has a curved portion formed therein that is curved from the front side to the rear side of the femur when viewed along the medial-lateral direction of the femur, and the curved portion is curved along the longitudinal direction of the femur when the intramedullary nail is inserted into the femur. A first reference line is a line on a reference plane that is a plane on which the posterior condyle of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the proximal side to the distal side and from the frontal view in which the posterior condyle is located downward, and is a line connecting the two posterior condyles. A second reference line is a line that is approximately perpendicular to the first reference line when viewed from the frontal view and passes through the first axis that is the axis of the one end side of the shaft portion. In the first angle, which is the angle formed by the second reference line and a first curve corresponding line that is a line connecting the first axis on the second reference line and the apex of the curved portion when viewed from the frontal view, when the apex of the curved portion is located in the medial direction when viewed from the second reference line, the first angle is a predetermined internal curve angle, or when the apex of the curved portion is located in the outward direction when viewed from the second reference line, the first angle is a predetermined external curve angle.

Note that the terms "front, back, inside, and outside" used here are all terms that are defined in terms of directions along a plane that crosses the human body. That is, the front-back direction is the direction along the sagittal plane, which is one of the planes that cross the human body, and the inside-out direction is the direction along the coronal plane, which is one of the planes that cross the human body. In addition, in the direction along the sagittal plane, the front side as seen from the human body is referred to as "front" or "forward" and the back side as seen from the human body is referred to as "back" or "backward". In addition, in the direction along the coronal plane, the direction toward the center of the human body is referred to as "inside" or "inner", and the direction away from the center of the human body is referred to as "outer" or "outer". In addition, the terms "proximal" and "distal" used here refer to the side closer to the center of the human body in the longitudinal direction of the bone as "proximal" and the direction away from the center of the human body as "distal".

The shaft portion is formed with a curved portion that curves from the front side to the rear side of the femur when viewed from the medial-lateral direction of the femur. This makes it easier to match the shape of the shaft portion to the lordotic shape of the femur seen in a lateral view of the femur when the intramedullary nail is placed at a desired position inside the femur. Note that the "lordotic shape" of the femur here refers to a shape in which the shaft curves forward with the apex of the curve on the front side when the femur is viewed from the side from the medial-lateral direction along the coronal plane of the human body.

In addition, regarding the curved portion, when the intramedullary nail is inserted into the femur, a first reference line is a line on a reference plane that is a surface on which the posterior condyles of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the front in a direction from the proximal side to the distal side along the longitudinal direction of the femur and from a direction in which the posterior condyle is located below, and is a line connecting the two posterior condyles, and a second reference line is a line that is approximately perpendicular to the first reference line when viewed from the front and passes through the first axis that is the axis of one end of the shaft portion. When the apex of the curved portion is located inwardly as viewed from the second reference line, the first angle is a predetermined inward curve angle, so that the inclination of the bending direction of the curved portion of the shaft portion with respect to the second reference line can be easily adapted to the inward curve shape of the femur. That is, the bending direction of the lordotic shape of the femur is inwardly inclined as viewed from the front with respect to the reference line B, which is a line that is approximately perpendicular to the reference line A connecting the posterior condyles (medial and lateral condyles) of the femur and passes through the positions of both ends of the center of the medullary cavity, as viewed from the front. The bending direction of the curved portion of the shaft portion is inclined in the same direction as the so-called "inward curve shape". This allows the intramedullary nail to be placed in an optimal position without any difficulty, even in a femur having an internal curvature.
In the following, the "front view seen from the direction from the proximal side to the distal side along the longitudinal direction of the femur and from the direction in which the posterior condyle is located below" will be simply referred to as "front view." The first axis, which is the axis of one end of the shaft portion, refers to the axis (center of the circular cross section) at the boundary with the one end of the shaft portion formed with the same diameter, that is, the distal portion of the main body.

In addition, with regard to the curved portion, when the intramedullary nail is inserted into the femur, a first reference line is a line on a reference plane that is a surface on which the posterior condyles of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the front in a direction from the proximal side to the distal side along the longitudinal direction of the femur and from a direction in which the posterior condyle is located downward, and is a line connecting the two posterior condyles, and a second reference line is a line that is approximately perpendicular to the first reference line when viewed from the front and passes through the first axis that is the axis of one end of the shaft portion. When the apex of the curved portion is located outward as viewed from the second reference line, the first angle is a predetermined lateral curvature angle, so that the inclination of the bending direction of the curved portion of the shaft portion with respect to the second reference line can be easily adapted to the lateral curvature shape of the femur. That is, the bending direction of the lordotic shape of the femur is inclined outward as viewed from the front with respect to the reference line B, which is a line that is approximately perpendicular to the reference line A connecting the posterior condyles (medial and lateral condyles) of the femur and passes through the positions of both ends of the center of the medullary cavity, and the bending direction of the curved portion of the shaft portion is inclined in the same direction as the so-called "lateral curvature shape" in which the bending direction of the lordotic shape of the femur is inclined outward as viewed from the reference line B. This allows the intramedullary nail to be comfortably placed in the optimal position even in femoral bones with an outwardly curved shape.

In addition, when the specified inward curvature angle is within the range of 1° to 25° at the first angle, it becomes easier to adapt the direction of curvature of the curved portion of the shaft to the angle of inclination commonly seen in inward curvature shapes.

In addition, when the specified outward curve angle is within the range of 1° to 25° at the first angle, it becomes easier to adapt the direction of the curve of the curved portion of the shaft to the angle of inclination commonly seen in outward curve shapes.

In addition, when the screw hole is inserted into the femur, in the range of the second angle, which is the angle between the first reference line and the direction of the screw hole, in a frontal view, the screw hole is positioned so that the direction of the screw hole is tilted backward with respect to the first reference line. If the second angle is within the range of 0° to 2°, the direction of the screw hole can be adjusted to the shape of the femur in which the so-called posterior torsion angle is tilted backward from the first reference line in the range of 0° to 2°. In other words, the lag screw can be easily adapted to the angle of the posterior torsion angle. As a result, even if the neck or head of the femur is tilted backward in a frontal view, the tip of the lag screw can be easily positioned near the center of the head. In addition, by setting the second angle within the range of 0° to 2°, it is easy to adapt to the angle of inclination commonly seen in the angle of the posterior torsion angle.

In addition, when the screw hole is inserted into the femur, in the range of the second angle, which is the angle between the first reference line and the direction of the screw hole, in a frontal view, the screw hole is positioned so that the direction of the screw hole is inclined forward with respect to the first reference line. If the second angle is within the range of 0° to 35°, the direction of the screw hole can be adjusted to the shape of the femur in which the so-called anteversion angle is inclined forward from the first reference line in the range of 0° to 35°. In other words, the lag screw can be easily adapted to the angle of the anteversion angle. As a result, even if the neck or head of the femur is inclined forward in a frontal view, the tip of the lag screw can be easily positioned near the center of the head. In addition, by setting the second angle within the range of 0° to 35°, it is easy to adapt to the angle of inclination commonly seen in the anteversion angle.

In addition, when the curved portion is formed to match the femur that curves forward with a radius of curvature within the range of 514 mm to 1358 mm in the range from the position just below the lesser trochanter to the position just above the patella when viewed from the medial-lateral direction of the femur, the shape of the shaft portion can be made to fit the lordotic shape of the femur as seen in a lateral view. In other words, by setting the curved portion of the shaft portion to match the lordotic shape of the femur with a radius of curvature within the range of 514 mm to 1358 mm, the intramedullary nail can be comfortably positioned in an optimal position on the femur.

In addition, the main body is formed with a total length in the range of 265 mm to 400 mm, and the curved portion is formed in the shaft portion. When the distance from the third reference line, which is the line corresponding to the position of the second axis, which is the axis of the proximal part of the main body, to the center position of the tip of the distal part of the main body is 13 mm or more when viewed along the medial-lateral direction of the femur, the position of the tip of the intramedullary nail can be more easily positioned in an appropriate position inside the femur (femoral medullary cavity) in accordance with the lordotic shape of the femur when the femur is viewed from the side. That is, for example, it is easier to prevent the intramedullary nail from coming into contact with the cortical bone while being inserted into the femur, or the tip of the intramedullary nail from protruding outward from the distal end of the femur when the tip of the intramedullary nail is inserted to the desired position on the distal side of the femur. As a result, the compatibility of the intramedullary nail with the femoral medullary cavity can be improved.

In addition, if the curved portion is composed of four bends, a first bend, a second bend, a third bend, and a fourth bend, and the curvature start position of the first bend is 120 mm from one end of the proximal portion of the body in the view along the medial-lateral direction of the femur, and the curvature radius of the range between the curvature start position of the first bend and the curvature start position of the second bend is 457 mm, the first bend can be adapted to the bone shape of the femur at the start of the curve of the lordotic shape in the process of advancing the tip of the intramedullary nail to the optimal depth beyond the position corresponding to the apex of the lordotic shape in the center of the medullary cavity of the femur. This reduces the contact between the intramedullary nail and the anterior cortical bone in the proximal portion of the femur, and allows the tip of the intramedullary nail to be smoothly inserted toward the distal direction of the femur. It also reduces the risk of fracture in the proximal femur and the risk of preventing the intramedullary nail from being inserted to the optimal depth. The optimal depth means the height at which the screw hole can be positioned near the center of the femoral head in the direction along the coronal plane.

In addition, when the curved portion is composed of four bends, a first bend, a second bend, a third bend, and a fourth bend, and when viewed from the inside-outside direction of the femur, the start position of the curve of the second bend is 150 mm from one end of the proximal portion of the main body, and the radius of curvature of the range between the start position of the curve of the second bend and the start position of the curve of the third bend is 475 mm, it becomes easier to form a shape corresponding to the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur. This makes it possible to easily insert the intramedullary nail into the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur and the position in the vicinity thereof. In addition, it becomes easier to adapt the portion beyond the second bend to the lordotic shape of the femur, and the intramedullary nail can be placed in an optimal position without difficulty.

In addition, if the curved portion is composed of four bends, namely, a first bend, a second bend, a third bend, and a fourth bend, and the curvature start position of the third bend is 175 mm from one end of the proximal body when viewed along the medial-lateral direction of the femur, and the curvature radius of the range between the curvature start position of the third bend and the curvature start position of the fourth bend is 637 mm, the third bend is easily shaped to correspond to the position where the bone starts to drop from the anterior side to the posterior side in the antegrade shape of the femur (the start point of the posterior curvature). This makes it easier to avoid excessive contact between the tip of the intramedullary nail and the anterior cortical bone in the distal part of the femur, and to guide the intramedullary nail to the center of the femoral medullary cavity. In addition, the portion beyond the third bend can be easily adapted to the lordotic shape of the femur, allowing the intramedullary nail to be placed in an optimal position without strain.

In addition, when the curved portion is composed of four bends, a first bend, a second bend, a third bend, and a fourth bend, and when viewed from the inside-outside direction of the femur, the start position of the curve of the fourth bend is 205 mm from one end of the proximal portion of the main body, and the radius of curvature of the range between the start position of the curve of the third bend and the start position of the curve of the fourth bend is 637 mm, the fourth bend can prevent the tip of the intramedullary nail from protruding from the anterior cortex in the area distal to the apex of the lordotic shape of the femur, which is a range with a larger curve in the lordotic shape, and the intramedullary nail can be inserted into the center of the femoral medullary cavity. This makes it possible to insert the lag screw into the optimal position in addition to inserting it into the center of the femoral medullary cavity, and to firmly fix the fracture.

In addition, when viewed from the front and before the start of insertion of the intramedullary nail into the femur, the direction in which the screw hole is formed is approximately parallel to the first reference line, and within the range of the third angle, which is the angle between the second reference line and the second curve corresponding line, which is the line connecting the first axis on the second reference line and the apex of the curved portion, the apex of the curved portion is located in the medial direction as viewed from the second reference line, and the third angle is within the range of 0° to 60°, or the apex of the curved portion is located outward as viewed from the second reference line. When the third angle is in the range of 0° to 27°, the intramedullary nail is inserted into the femur and rotated externally or internally by a predetermined angle during insertion, so that when the intramedullary nail is placed at a desired position on the femur, the second curvature corresponding line can be tilted outward or inward with respect to the second reference line when viewed from the front, and the direction of the screw hole can be tilted forward or backward with respect to the first reference line. That is, the curved portion of the shaft portion can be curved externally or internally with respect to the external curvature shape or internal curvature shape of the femur, and the direction of the lag screw can be aligned with the antetorsion angle or posterior curvature angle of the femur, so that the intramedullary nail can be adapted to the femur. This allows the intramedullary nail to be adapted to the direction of curvature of the antetorsion shape of the femur and the antetorsion angle or posterior curvature angle, and can be positioned at an optimal position without difficulty. In addition, before the intramedullary nail is inserted into the femur, the direction in which the screw holes are formed is approximately parallel to the first reference line when viewed head-on; that is, the direction in which the screw holes are formed is not tilted at a certain angle in advance with respect to the anteversion angle. Therefore, even if the intramedullary nail is rotated outward or inward during insertion, the position of the tip of the lag screw is prevented from shifting from near the center of the femoral head.

In addition, when the apex of the curved portion is located in the medial direction as viewed from the second reference line and the third angle is 7°, the intramedullary nail is inserted into the femur and rotated outward by 12° along the way, so that when the intramedullary nail is placed in the desired position of the femur, the second curve corresponding line is inclined 5° outward (5° outward curve) with respect to the second reference line when viewed from the front, and the direction of the screw hole is inclined 12° forward with respect to the first reference line. That is, the curved portion of the shaft is outwardly curved 5° with respect to the femur having a 5° outward curve shape and an anterior torsion angle of 12°, and the direction of the lag screw can be adapted to an anterior torsion angle of 12°. This allows the intramedullary nail to be comfortably positioned in an optimal position by adapting it to the lordotic shape and anterior torsion angle of the femur. In addition, before the intramedullary nail is inserted into the femur, the direction of the screw hole is approximately parallel to the first reference line when viewed from the front. In other words, the direction of the screw hole is not tilted by a certain angle in advance with respect to the anteversion angle. Therefore, even if the intramedullary nail is externally rotated 12° during insertion, the tip position of the lag screw is prevented from shifting forward from near the center of the femoral head. In addition, with this intramedullary nail, before it is inserted into the femur, the curved portion of the shaft is curved inward by 7° when viewed from the front.

In addition, when viewed from the front and before the start of insertion of the intramedullary nail into the femur, in the range of a third angle, which is the angle between the second reference line and a second curve corresponding line, which is a line connecting the first axis on the second reference line and the apex of the curved portion, the second reference line, the apex of the curved portion is located in the medial direction as viewed from the second reference line, and the third angle is within a range of 1° to 25°, or the apex of the curved portion is located in the lateral direction as viewed from the second reference line, and the third angle is within a range of 1° to 25°, and in the range of a fourth angle, which is the angle between the first reference line and the formation direction of the screw hole, the screw hole is located in the medial direction as viewed from the first reference line. When the first reference line is used as a reference and the direction of the screw hole is inclined forward and the fourth angle is within a range of 0° to 35°, or the direction of the screw hole is inclined backward with respect to the first reference line and the fourth angle is within a range of 0° to 2°, when the intramedullary nail is inserted into the femur without external or internal rotation and the intramedullary nail is placed at a desired position of the femur, the second curvature corresponding line can be inclined outward or inward with respect to the second reference line when viewed from the front, and the direction of the screw hole can be inclined forward or backward with respect to the first reference line. That is, the intramedullary nail can be adapted to the femur by externally or internally curving the curved portion of the shaft portion with respect to the external or internal curvature shape of the femur and by aligning the direction of the lag screw with the antetorsion angle or posterior totorsion angle of the femur. This allows the intramedullary nail to be placed in an optimal position without strain, in accordance with the direction of the femoral lordotic curvature and the anteversion angle or retroversion angle. The intramedullary nail can also be inserted into the femur without external or internal rotation. Furthermore, before the intramedullary nail is inserted into the femur, the direction in which the screw hole is formed is inclined in advance to the anterior or posterior side with respect to the first reference line when viewed from the front, so that simply inserting the intramedullary nail straight to the desired position allows the lag screw to correspond to the anteversion angle or retroversion angle, and the position of the tip of the lag screw can be prevented from shifting from near the center of the femoral head.

In addition, when the apex of the curved portion is located in the outward direction as viewed from the second reference line, the third angle is 5°, the screw hole formation direction is inclined forward with respect to the first reference line, and the fourth angle is 12°, when the intramedullary nail is inserted into the femur without external rotation and placed in the desired position of the femur, the second curve corresponding line can be inclined 5° outward (5° outward curve) with respect to the second reference line when viewed from the front, and the screw hole formation direction can be inclined 12° forward with respect to the first reference line. That is, the curved portion of the shaft can be outwardly curved 5° with respect to the femur having a 5° outward curve shape and an anterior torsion angle of 12°, and the direction of the lag screw can be adapted to an anterior torsion angle of 12°. This allows the intramedullary nail to be comfortably positioned in an optimal position by adapting it to the lordotic shape and anterior torsion angle of the femur. In addition, the intramedullary nail can be inserted into the femur without external rotation. In addition, before the intramedullary nail is inserted into the femur, the direction of the screw hole is inclined 12° forward from the first reference line when viewed from the front. Therefore, simply inserting the intramedullary nail straight to the desired position allows the lag screw to accommodate an anteversion angle of 12°, and the position of the tip of the lag screw can be prevented from shifting forward from near the center of the femoral head. In addition, in this intramedullary nail, before it is inserted into the femur, the curved portion of the shaft is curved outward by 5° when viewed from the front.

The intramedullary nail of the present invention can prevent problems that occur during the surgical procedure for fractures of the proximal femur, and can be placed in an ideal position within the femur to connect and firmly fix bone fragments.

FIG. 1A is a schematic diagram showing the anteversion angle of the femur as viewed from the proximal to the distal side of the femur, and FIG. 1B is a schematic diagram showing the coronal, sagittal, and transverse planes that cross the human body. 1A is a schematic side view showing the shape of a right femur when viewed from the inside to the outside in the medial-lateral direction along the coronal plane of the human body (side view), and FIG. 1B is a schematic front view showing the shape of a right femur when viewed from the front to the back in the anterior-posterior direction along the sagittal plane of the human body (front view). FIG. 2 is a schematic diagram showing the lateral curvature shape of the femur. FIG. 1A is a diagram showing the state in which the posterior condyle of the femur and the posterior edge of the greater trochanter of the femur are located on the same plane (reference plane); FIG. 1B is a diagram showing the position of the posterior condyle and the position of the posterior edge of the greater trochanter of the femur when viewed from the outside to the inside along the medial-lateral direction; and FIG. 1C is a diagram showing the position of the posterior condyle when viewed from the distal side to the proximal side along the longitudinal direction of the femur. FIG. 2 is a schematic diagram showing the internal curvature shape of the femur. 1A to 1D are diagrams showing the shape of a conventional intramedullary nail, and FIG. 1E is a diagram showing the positional relationship between the external curvature shape of the femur and the bending direction of the curved portion of the shaft. FIG. 1A is a schematic diagram showing a conventional intramedullary nail inserted into a femur with its tip in contact with the femoral cortical bone, and FIG. 1B is a schematic diagram showing the conventional intramedullary nail being externally rotated and being inserted toward the distal end. FIG. 1A is a schematic diagram showing a state in which the tip position of the lag screw in a conventional intramedullary nail is forward of the center of the femoral head, and FIG. 1B is a schematic diagram showing a state in which a gap occurs between the bone fragments to be fixed when the femur is compressed from the outside. FIG. 1A is a front view of a bone fastening device having an intramedullary nail according to a first embodiment of the present invention, and FIG. 1B is a side view of the bone fastening device looking from the outside to the inside. FIG. 2 is a view showing a state in which the bone setting tool is inserted into a desired position of the femur. FIG. 2A is a front view of the intramedullary nail as viewed from the front to the rear, and FIG. 2B is a side view of the intramedullary nail as viewed from the inside to the outside. FIG. 2 is a schematic view of the intramedullary nail viewed from the base end to the tip end just before the intramedullary nail is inserted into the femur. FIG. 2 is a schematic diagram showing the state in which the intramedullary nail has been inserted into the femur and externally rotated 12° from the front. 1A and 1B are diagrams showing the positions of four bend portions in the shaft portion of an intramedullary nail, where (aa) is a front view of the intramedullary nail looking from the front to the rear, and (b) is a side view of the intramedullary nail looking from the outside to the inside. FIG. 4 is a schematic enlarged view showing four bend portions. 13 is a diagram showing the correspondence between the point where the bone begins to bend in the lordotic shape of the femur and the curvature start position of the first bend portion of the intramedullary nail. FIG. 13 is a diagram showing the correspondence between the apex of the bone bend in the lordotic shape of the femur and the curvature start position of the second bend portion of the intramedullary nail. FIG. 13 is a diagram showing the correspondence between the anterior cortical bone of the femur and the curvature start position of the third bend portion of the intramedullary nail. FIG. FIG. 13 is a diagram showing the correspondence between the range of greater curvature in the lordotic shape of the femur and the curvature start position of the fourth bend portion of the intramedullary nail. FIG. 2A is a front view of a bone synthesis device having an intramedullary nail according to a second embodiment of the present invention, and FIG. 2B is a side view of the bone synthesis device looking from the front to the rear, and FIG. FIG. 2A is a front view of the intramedullary nail as viewed from the front to the rear, and FIG. 2B is a side view of the intramedullary nail as viewed from the outside to the inside.

Hereinafter, embodiments of the present invention will be described for the purpose of understanding the present invention.
In the following, the terms "anterior (front)", "posterior (rear)", "internal (inner)", and "external (outer)" are all used as terms indicating the respective directions along a plane that crosses the human body, as described above. In the following, with respect to the intramedullary nail (or shaft), the part of the intramedullary nail that is proximal to the trunk of the patient to be treated is referred to as the "base end side", and the part of the intramedullary nail that is distal to the trunk of the patient to be treated is referred to as the "distal end side".

When the femur is viewed from the side with reference to Figure 2(a), the shape in which the shaft curves forward with the apex P of the curve on the forward side is referred to as a "lordotic shape."

With reference to Figure 3, the viewpoint seen from the proximal side to the distal side along the longitudinal direction of the femur and from the direction in which the posterior condyle is located below is referred to as the "front view." With reference to Figure 3, the line connecting the posterior condyles (medial condyle F3 and lateral condyle F4) in the front view is referred to as the "reference line A," and the line that is approximately perpendicular to this reference line A and passes through position M1 at both ends of the center of the medullary cavity is referred to as the "reference line B."

Furthermore, with reference to FIG. 3, when viewed from the front, the direction of curvature in the lordotic shape with respect to the reference line B is inclined outward when viewed from the reference line B, and this is referred to as an "external curvature shape."

In addition, when viewed from the front, the inclination of the lordotic shape relative to the reference line B is referred to as an "internal curvature shape" when the direction of the lordotic shape is inclined inward when viewed from the reference line B.

[First embodiment of the present invention]
9(a) and 9(b), an intramedullary nail 1, which is an example of an intramedullary nail to which the present invention is applied, is a member used in combination with a lag screw 2, a sub-pin 3, a locking screw 4, a locking screw 5, a set screw (not shown), and an end cap (not shown) during surgery. Each member constitutes a bone setting tool A.

Figure 9(a) is a front view of the bone fastening device A from the front to the rear, and Figure 9(b) is a side view of the bone fastening device A from the outside to the inside.

In this embodiment, each component of the bone setting tool A is preferably made of a titanium alloy, but is not limited to this and may be made of known materials that have excellent biocompatibility and high fatigue strength, such as alloys of aluminum and vanadium, stainless steel, various engineering plastics, etc. Also, each component constituting the bone setting tool may be made of a different material.

The intramedullary nail 1 is inserted from its tip toward the distal side of the femur, and is a component that connects bone fragments so that they do not shift and adhere to each other or separate before the fracture heals. The intramedullary nail 1 is also a component that holds a lag screw 2 or the like inserted into the bone.

The intramedullary nail 1 is a component for the left femur. The following description will be based on the intramedullary nail 1, but the intramedullary nail to which the present invention is applied can also be applied to an intramedullary nail for the right femur. The intramedullary nail for the right femur has a shape that corresponds to the lordotic shape, anteversion angle (retroversion angle), and lateral curvature shape (internal curvature shape) of the right femur, but the basic structure is the same as that of the intramedullary nail 1.

The lag screw 2 is a component that connects bone fragments together to prevent them from slipping and adhering or becoming separated until the fractured area heals.

The sub-pin 3 is a component that protrudes into the fracture site to connect the fractured bone fragments. The sub-pin 3 bites into the cancellous bone and generates resistance to the rotational force applied to the bone fragments of the bone to be treated, and works together with the lag screw 2 to prevent the bone fragments from rotating.

The locking screws 4 and 5 are members that fix the lower end of the intramedullary nail 1 to the bone to be treated. In this embodiment, the locking screws 4 and 5 are used in only two places, but this is not limited to this, and the number of screws that can be used as needed can be determined according to the number of transverse holes (reference numbers omitted) formed in the intramedullary nail 1, etc.

The bone fixing device A also has a set screw (not shown). The set screw is a member provided above and inside the longitudinal hole of the intramedullary nail 1, and by engaging with the lag screw 2, it holds the lag screw 2 so that it does not move backward and fall out, and also suppresses the rotation of the lag screw 2.

Figure 10 shows the state in which the bone setting tool A has been inserted into the desired position (optimum depth) of the femur F. Figure 10 is a front view of the femur F and the bone setting tool A, looking from the front to the rear. The femur shown in Figure 10 is the left femur.

As shown in FIG. 10, the tip of the intramedullary nail 1 is inserted into the femoral shaft F5 at a position near the distal femur F7. The tip of the lag screw 2 is inserted into the proximal femur F8 at a position near the center of the femoral head F1.

The shape of the intramedullary nail 1 will be explained in detail.

11(a) and 11(b) show only the intramedullary nail 1, with FIG. 11(a) corresponding to FIG. 9(a) and FIG. 11(b) corresponding to FIG. 9(b). Also, FIG. 11(a) and FIG. 11(b) show a simulated view of the position of the tip of the lag screw 2 when the lag screw 2 is inserted into the intramedullary nail 1, indicated by the reference symbol 2a.

As shown in Figures 11(a) and 11(b), the intramedullary nail 1 is composed of a proximal body portion 10, a shaft portion 11, and a distal body portion 12. The intramedullary nail 1 is a cylindrical body having a long axial hole (not shown) that runs through the inside along its longitudinal axis.

The proximal body portion 10 is a member that constitutes the base end side of the intramedullary nail 1. The proximal body portion 10 is formed with a screw hole 100 for inserting the lag screw 2 and a pin hole 101 for inserting the sub-pin 3. The direction in which the screw hole 100 is formed will be described later.

The screw hole 100 and the pin hole 101 are also formed to intersect with the longitudinal hole that passes through the inside of the intramedullary nail 1.

In addition, a set screw (not shown) is built into the base end of the proximal body portion 10.

The proximal body portion 10 has a uniform diameter portion 10a formed with a substantially uniform outer diameter, and a reduced diameter portion 10b whose outer diameter gradually decreases toward the shaft portion 11. The axis of the end of the shaft portion 11 connected to the reduced diameter portion 10b of the proximal body portion 10, which constitutes part of this cylindrical body (the axis of the starting position of the shaft portion 11), corresponds to the "first axis, which is the axis of one end side of the shaft portion" in the claims of this application.

The shaft portion 11 extends along the longitudinal direction of the intramedullary nail 1. The shaft portion 11 is also formed with a curved portion 110 (see FIG. 11(b)).

This curved portion 110 is used to position the intramedullary nail 1 along the lordotic and lateral curvatures of the femur when the intramedullary nail 1 is inserted into a predetermined position in the femur. The details of the bending of the curved portion 110 will be described later.

In addition, two lateral holes 111 and lateral hole 112 are formed on the distal body part 12 side of the shaft part 11. Each hole is a hole for inserting the locking screw 4 and the locking screw 5, respectively, and is formed to intersect with the long axis hole that penetrates the inside of the intramedullary nail 1.

In addition, the direction in which the lateral stop hole 111 is formed and the direction in which the lateral stop hole 112 is formed are different directions.

Here, the formation direction of the lateral stop hole 111 and the formation direction of the lateral stop hole 112 do not necessarily have to be different. However, it is preferable that the formation direction of the lateral stop hole 111 and the formation direction of the lateral stop hole 112 are different from each other, since the bone connection tool A can be more firmly fixed to the bone to be treated by changing the direction in which the two locking screws 4 and 5 are inserted.

The distal body portion 12 is a member that constitutes the tip side of the intramedullary nail 1. The distal body portion 12 is formed so that the outer diameter gradually decreases toward the tip. The tip of the distal body portion 12 is the opening 120 of a long axial hole that penetrates the inside of the intramedullary nail 1.

Next, we will explain the formation direction of the screw hole 100, which corresponds to the anteversion angle of the femur, and the bending direction of the curved portion 110 of the shaft portion 11, which corresponds to the lateral curvature shape of the femur.

First, the direction of the screw hole 100 through which the lag screw 2 is inserted in the intramedullary nail 1 is formed in the left-right direction when the intramedullary nail 1 is viewed from the base end toward the tip end (corresponding to the front view described above) immediately before the intramedullary nail 1 is inserted into the femur (see FIG. 12).

More specifically, in FIG. 12, the screw holes 100 are formed in the left-right direction in the figure (the direction connecting 3 o'clock and 9 o'clock in the circumferential direction of a clock). In addition, when it is assumed that there is a horizontal plane below the intramedullary nail 1, the angle between the horizontal plane and the direction in which the screw holes 100 are formed is 0° (approximately parallel).

The direction of curvature of the curved portion 110 of the shaft portion 11 is such that, immediately before the intramedullary nail 1 is inserted into the femur, when the intramedullary nail 1 is viewed from the base end toward the tip end (corresponding to the above-mentioned head-on view), the "vertical line L3" passing through the axis of the starting position of the shaft portion 11 and the "curve corresponding line L4" connecting the axis of the starting position of the shaft portion 11 and the apex of the curve of the curved portion 110 are positioned on the inside of the vertical line L3 as viewed from the femur, and the angle between the vertical line L3 and the curve corresponding line L4 is 7° (see FIG. 12). This direction of curvature of the curved portion 110 is called a "7° inward curve".

In addition, in FIG. 12, the lag screw 2, locking screw 4, and locking screw 5 are attached to the intramedullary nail 1 to easily visualize the direction in which the screw hole 100 is formed and the direction in which the curved portion 110 of the shaft portion 11 is bent just before the intramedullary nail 1 is inserted into the femur.

In actual surgery, as described below, the intramedullary nail 1 is inserted into the femur, externally rotated, and with the intramedullary nail 1 in a predetermined position, the lag screw 2, locking screw 4, and locking screw 5 are inserted, so that no components are inserted into the intramedullary nail 1 before it is inserted into the femur.

In this way, the intramedullary nail 1 has the direction of formation of the screw hole 100 described above (0°, approximately parallel to the horizontal plane) and the direction of curvature of the curved portion 110 of the shaft portion 11 (7° inward curvature).

During the procedure, the intramedullary nail 1 is inserted into the femur from its tip, and viewed from the front, the operator externally rotates the intramedullary nail 1 by 12° (rotating the intramedullary nail outward around the axis of the starting position of the shaft portion 11), so that the angle between the direction in which the screw hole 100 is formed and the reference line A is 12°. Also, the angle between the curve corresponding line L4 and the reference line B is 5°, and the direction of curvature of the curved portion 110 of the shaft portion 11 is a 5° outward curve (see FIG. 13). In FIG. 13, the axis of the starting position of the shaft portion 11 is indicated by the symbol G, and the apex of the curvature of the curved portion 110 is indicated by the symbol E.

In other words, by inserting the intramedullary nail 1 into the femur and externally rotating it by 12°, it can be positioned to fit the femur, which has an anteversion angle of 12° and a 5° external curvature.

That is, for a femur with an anteversion angle of 12°, the intramedullary nail 1 can position the tip of the lag screw 2 near the center of the femoral head F1. In addition, the position of the tip of the lag screw 2 can be prevented from moving toward the anterior side of the femoral head F1.

In addition, the intramedullary nail 1 can align the direction of the curved portion 110 of the shaft portion 11 with the femur, which has a 5° external curvature. This improves the compatibility of the shaft portion 11 with the femur.

Here, the intramedullary nail to which the present invention is applied is not necessarily limited to a case in which the angle between the horizontal plane and the direction in which the screw hole 100 is formed is set to 0° (approximately parallel) when viewed from the front, and the intramedullary nail is externally rotated 12° after insertion into the femur and placed on the femur. This point can be designed and placed according to the anteversion angle of the femur. Here, the angle between the horizontal plane and the direction in which the screw hole 100 is formed, and the angle at which the intramedullary nail is externally rotated (or internally rotated) can be set preferably within a range of -2° to 35° with respect to the reference line A, which is a commonly seen numerical range for the anteversion angle and posterior rotation angle.

In addition, the intramedullary nail to which the present invention is applied is not necessarily limited to a 7° inward bend direction of the curved portion 110 when viewed from the front, and an external rotation of 12° after insertion into the femur, so that the intramedullary nail is placed in the femur. This can be designed and placed according to the external or internal curve shape of the femur and its angle. Here, the direction and angle of the curved portion 110 and the angle at which the intramedullary nail is externally (or internally) rotated can be set within a typical numerical range for the femur, which is an internal curve shape of 1° to 25°, or an external curve shape of 1° to 25°.

In this way, the intramedullary nail 1 has a unique structure in the direction in which the screw hole 100 is formed (0°, approximately parallel to the horizontal plane) and in the direction of curvature of the curved portion 110 of the shaft portion 11 (7° internal curvature), which sufficiently enhances compatibility with femora having a certain anteversion angle and external curvature shape.

In addition, in the case of an intramedullary nail to which the present invention is applied, for example, an intramedullary nail can be designed using the combination of values shown in Tables 1 to 6 below, and inserted into the femur to achieve the desired anteversion angle or posterior rotation angle and a position that is suitable for a femur having an external or internal curvature shape.

Here, for each combination of values shown in Tables 1 to 6, the direction in which the screw hole 100 is formed is 0°, approximately parallel to the horizontal plane, when viewed from the front, immediately before the intramedullary nail 1 is inserted into the femur.

For example, in Table 1, if the bend of the curved portion of the shaft portion 11 before insertion into the femur is 0° (no external or internal curvature), then by inserting it into the femur and externally rotating it 1°, an intramedullary nail with an anteversion angle of 1° and corresponding to a femur externally curved 1° will be obtained.

For example, in Table 3, if the curved portion of the shaft portion 11 before insertion into the femur is bent 2° inward, then by inserting it into the femur and externally rotating it 1°, an intramedullary nail with an anteversion angle of 1° and corresponding to a femur with an internal curvature of 1° will be obtained.

Furthermore, for example, in Table 5, if the curved portion of the shaft portion 11 before insertion into the femur is bent at 3° external curvature, then by inserting it into the femur and internally rotating it by 2°, an intramedullary nail with a posterior torsion angle of 2° and corresponding to a femur with an external curvature of 1° will be obtained.

In this way, the intramedullary nail of the present invention can be inserted into the femur and positioned to suit the femur having the desired anteversion or retroversion angle and external or internal curvature.

The combinations of values in Tables 1 to 3 above can be applied not only to intramedullary nails for left femurs, but also to intramedullary nails for right femurs.

In addition, the direction of the screw hole 100 does not necessarily have to be 0°, which is approximately parallel to the horizontal plane when viewed from the front, immediately before the intramedullary nail 1 is inserted into the femur. For example, by changing the angle with respect to the horizontal plane, the direction and angle of bending of the curved portion of the shaft portion 11 and the direction and angle of rotation after insertion can be appropriately set according to the anteversion angle or posterior torsion angle and the external or internal curvature shape of the target femur.

Next, we will explain the direction of curvature of the curved portion 110 of the shaft portion 11, which corresponds to the lordotic shape of the femur.

First, the intramedullary nail 1 is formed to have a length of 265 mm from its base end 13 to its tip end 14. In addition, the curved portion 110 of the shaft portion 11 has four bends (curves) along the longitudinal direction, forming the overall curve.

In Fig. 14(a) and Fig. 14(b), the start positions of curvature are indicated by symbols A to D for the first bend, the second bend, the third bend, and the fourth bend, respectively. Fig. 14(a) is a front view of the intramedullary nail 1 viewed from the front to the rear. Fig. 14(b) is a side view of the intramedullary nail 1 viewed from the outside to the inside.

As shown in FIG. 14(b), the curved portion 110 of the shaft portion 11 of the intramedullary nail 1 is curved from the left side to the right side as a whole in the figure, and this curve corresponds to the curve from the front to the back in the lordotic shape of the femur. Note that FIG. 14(a) and FIG. 14(b) show an intramedullary nail for the left femur, but in the intramedullary nail for the right femur, the curved portion of the shaft corresponds to the curve from the front to the back in the lordotic shape of the femur, just like the left one.

In addition, because the curved portion 110 of the intramedullary nail 1 is curved, when viewed from the side, the distance h between the reference line L5, which corresponds to the extension of the axis of the proximal body portion 10, and the center position of the tip 14 is 15 mm.

The curvature start position A of the first bend is 120 mm away from the base end 13 of the intramedullary nail 1. The curvature start position B of the second bend is 150 mm away from the base end 13 of the intramedullary nail 1. The curvature start position C of the third bend is 175 mm away from the base end 13 of the intramedullary nail 1. The curvature start position D of the fourth bend is 205 mm away from the base end 13 of the intramedullary nail 1.

As shown in FIG. 15, in the intramedullary nail 1, the radius of curvature between positions A and B is 457.2055 mm, the radius of curvature between positions B and C is 475.1435 mm, and the radius of curvature between positions C and D is 637.797 mm. The radius of curvature between positions A and C is 439.8625 mm, and the radius of curvature between positions B and D is 543.8545 mm.

In this way, the intramedullary nail 1 has four bends that define the overall curvature of the curved portion 110. In addition, by forming these four bends, the distance h between the reference line L5 and the center position of the tip 14 of the intramedullary nail 1 is 15 mm.

Here, the intramedullary nail 1 is not necessarily limited to a length of 265 mm from its base end 13 to its tip end 14, and the length can be set as appropriate. In addition, it is preferable that the total length of the intramedullary nail to which the present invention is applied is set in the range of 265 mm to 400 mm. Furthermore, by setting the total length to 265 mm, it becomes easier to adapt to the approximately average length of the femur of elderly Japanese people, especially women.

In addition, the curved portion 110 of the shaft portion 11 of the intramedullary nail 1 does not necessarily have to be bent at four locations along the longitudinal direction to form an overall curve, and the curvature of the curved portion can be set as appropriate. In addition, it is preferable that the curved portion be curved in a range from just below the lesser trochanter to just above the patella, which is the general numerical range of the lordotic shape of the femur, with a curvature radius of 514 mm to 1358 mm.

In addition, the intramedullary nail 1 is not necessarily limited to a distance h between the reference line L5 corresponding to the extension of the axis of the proximal body 10 and the center position of the tip 14 being 15 mm when viewed from the side due to the formation of the bend in the curved portion 110, and can be set appropriately. However, by setting the total length of the intramedullary nail 1 to 265 mm and the distance h to 15 mm, it becomes easier to position the tip of the intramedullary nail at an appropriate position inside the femur (femoral medullary cavity) in accordance with the approximately average length and lordotic shape of the femur of elderly Japanese people, especially women. In addition, in the present invention, it is preferable that the distance h between the reference line corresponding to the extension of the axis of the proximal body and the center position of the tip be set to 13 mm or more depending on the total length of the intramedullary nail.

In addition, the relationship between the total length of the intramedullary nail and the distance h between the reference line L and the center position of the tip of the intramedullary nail can be set as follows, according to the length of the femur of the patient to be treated. As an example, the total length of the intramedullary nail can be set to 300 mm to 320 mm and the distance h to 17 to 22 mm, or the total length of the intramedullary nail can be set to 340 mm to 360 mm and the distance h to 22 to 25 mm.

In addition, for the four bends in the curved portion 110 of the shaft portion 11, the distance from the base end of the intramedullary nail 1 to the start position of each bend and the value of the radius of curvature can be set appropriately. However, by designing the intramedullary nail 1 as described above, the following effect occurs.

First, the curvature start position A of the first bend portion is 120 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions A and B is set to 457.2055 mm in side view. This allows the first bend portion to conform to the bone shape of the femur at the start of the lordotic curve as the tip 14 of the intramedullary nail advances to the optimal depth beyond the position corresponding to the apex of the lordotic curve in the center of the femoral medullary cavity.

This reduces contact between the intramedullary nail 1 and the anterior cortical bone F9 in the proximal part of the femur, allowing the tip 14 of the intramedullary nail 1 to be smoothly inserted toward the distal direction of the femur. It also reduces the risk of fracture in the proximal part of the femur and the risk of preventing the intramedullary nail from being inserted to the optimal depth.

In this regard, in FIG. 16, reference symbol A indicates the start position of the curvature of the first bend portion, and reference symbol F9 indicates the anterior cortical bone in the proximal femur.

In addition, the curvature start position B of the second bend is 150 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions B and C is set to 475.1435 mm in side view, making it easier to form a shape that corresponds to the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur.

This makes it possible to easily insert the intramedullary nail into the position corresponding to the apex of the lordotic shape in the center of the medullary cavity of the femur and the area nearby. In addition, the portion beyond the second bend can be easily adapted to the lordotic shape of the femur, allowing the intramedullary nail 1 to be comfortably positioned in the optimal position.

In this regard, in FIG. 17, the symbol B indicates the start position of the curvature of the second bend, and the symbol M2 indicates the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur.

In addition, the curvature start position C of the third bend is 175 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions C and D is set to 637.797 mm in side view, which makes it easier to give the third bend a shape that corresponds to the position where the bone begins to drop from the anterior side to the posterior side in the lordotic shape of the femur (the start point of the posterior curvature).

This avoids excessive contact between the tip 14 of the intramedullary nail 1 and the anterior cortical bone F10 in the distal part of the femur, making it easier to guide the intramedullary nail to the center of the femoral medullary cavity.

In this regard, in FIG. 18, reference symbol C indicates the start position of the curvature of the third bend section, and reference symbol F10 indicates the anterior cortical bone.

The curvature start position D of the fourth bend is 205 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions C and D is set to 637.797 mm in side view. This prevents the tip 14 of the intramedullary nail 1 from protruding from the anterior cortex in the area T of the lordotic shape of the femur that is distal to the apex of the lordotic shape, where the curvature is greater, and makes it possible to insert the intramedullary nail into the center of the femoral medullary cavity.

This allows the lag screw to be inserted into the center of the femoral medullary cavity and into the optimal position, firmly fixing the fracture.

In this regard, in FIG. 19, the symbol D indicates the start position of the curvature of the fourth bend, the symbol M2 indicates the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur, and the symbol T indicates the area distal to the apex of the lordotic shape of the femur, that is, the area with a greater curvature within the lordotic shape.

In this way, by setting the positions and curvatures of the four bends in the curved portion 110 of the shaft portion 11, the intramedullary nail 1 can be fully adapted to the shape of the lordotic curve of the femur.

Next, we will briefly explain the procedure for inserting the intramedullary nail 1 according to the present invention into the femur.

(1) A hole is drilled from the proximal to distal side of the femoral shaft with a reamer, and the intramedullary nail 1 is inserted into the hole.

(2) The tip of the intramedullary nail 1 is inserted to a specified position inside the femur (femoral medullary cavity), and the intramedullary nail 1 is externally rotated 12° together with the target device to which the intramedullary nail 1 is attached. When viewed head-on, the direction of the screw hole 100 is aligned with the antetorsion angle of the femur, and the direction of the bend of the curved portion 110 of the shaft 10 is externally rotated 5°. In addition, an X-ray device is used to fine-tune the position of the screw hole 100 of the inserted intramedullary nail 1.

(3) Drill a hole on the side of the femur related to the intended insertion site of the lag screw 2, insert the lag screw 2 into the hole, and insert it through the screw hole 100 of the intramedullary nail 1 until the tip of the lag screw 2 reaches near the center of the femoral head F1.

(4) After the tip of the lag screw 2 reaches near the center of the femoral head F1, the fitting protrusion of the set screw built into the upper part of the long axial hole of the intramedullary nail 1 is inserted into the long groove of the lag screw 2 and pressed from above to fix the lag screw 2.

(5) Drill a hole on the side of the femur related to the intended insertion site of the sub-pin 3, insert the sub-pin 3 into the hole, and pass it through the pin hole 101 of the intramedullary nail 1 and the pin hole of the set screw placed in the intramedullary nail 1.

(6) An end cap is further attached to the top of the inserted set screw to prevent the sub-pin 3 from coming off the intramedullary nail 1.

By following the above steps, the bone connection device A having the intramedullary nail 1 is inserted into the femur to be treated, and the fracture site on the proximal side of the femur can be firmly fixed with the bone connection device A.

The main advantages of this embodiment are as follows:

First, in the intramedullary nail 1, when viewed from the front, the direction of curvature of the curved portion 110 of the shaft portion 11 can be externally rotated by 5° to match the external curvature of the femur F. This allows the intramedullary nail 1 to be adapted to the external curvature of the femur F.

When inserting the intramedullary nail 1 into the femur F from the tip 14, the nail can be easily inserted by externally rotating the nail 1 by 12°. This external rotation of the nail 1 by 12° also allows the direction of curvature of the curved portion 110 of the shaft portion 11 to assume an external curvature angle of 5° when viewed from the front.

Furthermore, by performing this 12° external rotation, the angle that the screw hole 100 forms with the reference line A can be set to 12° when viewed head-on, so that the direction in which the screw hole 100 is formed corresponds to the anteversion angle of the femur F.

In addition, during this 12° external rotation operation, the direction in which the screw hole 100 is formed is such that the tip of the lag screw 2 is positioned near the center of the femoral head F1, preventing the tip of the lag screw 2 from being positioned on the anterior side of the femoral head F1.

This also makes it possible to avoid the task of compressing the femur from the outside to reposition the tip of the lag screw 2 near the center of the femoral head F1 in response to a misalignment of the tip of the lag screw 2. This prevents gaps from appearing between the bone fragments to be fixed due to compression, and prevents the knee from internally rotating and becoming excessively anteverted.

In addition, in the intramedullary nail 1, the curved portion 110 of the shaft portion 11 is formed with four bent portions, and by setting the position and curvature of each bent portion, the intramedullary nail 1 can be fully adapted to the shape of the lordotic curve of the femur.

[Second embodiment of the present invention]
Next, an intramedullary nail 1a according to a second embodiment of the present invention will be described. In the following description, features different from the first embodiment of the present invention will be described, and the same reference numerals will be used to designate the same members as those in the first embodiment, and detailed description thereof will be omitted.

As shown in Figures 20(a) and 20(b), an intramedullary nail 1a, which is an example of an intramedullary nail to which the present invention is applied, is a component used in combination with a lag screw 2, a sub-pin 3, a locking screw 4, a locking screw 5, a set screw, and an end cap during surgery. Each component constitutes a bone setting device B.

Figure 20(a) is a front view of the bone fastening device B seen from the front to the rear. Figure 20(b) is a side view of the bone fastening device B seen from the outside to the inside.

21(a) and 21(b) show only the intramedullary nail 1a, with 21(a) corresponding to 20(a) and 21(b) corresponding to 20(b). 21(a) and 21(b) also show a simulated view of the position of the tip of the lag screw 2 when the lag screw 2 is inserted into the intramedullary nail 1a, indicated by the reference symbol 20a.

As shown in Figures 21(a) and 21(b), the intramedullary nail 1a is composed of a proximal body portion 7, a shaft portion 8, and a distal body portion 9. The intramedullary nail 1a is a cylindrical body having a long axial hole (not shown) that runs through the inside along its longitudinal axis.

The proximal body portion 7 is also formed with a screw hole 100a for inserting the lag screw 2 and a pin hole 101 for inserting the sub-pin 3. The direction in which the screw hole 100a is formed will be described later.

The screw hole 100a and the pin hole 101 are also formed to intersect with the long axis hole that passes through the inside of the intramedullary nail 1a.

In addition, a set screw (not shown) is built into the base end of the proximal body part 7.

The shaft portion 8 also has a curved portion 110a (see Figure 21 (b)).

This curved portion 110a is used to position the intramedullary nail 1a along the antegrade and lateral curvature of the femur when the intramedullary nail 1a is inserted into a predetermined position in the femur. The details of the curvature of the curved portion 110a will be described later.

In addition, two lateral stop holes 111 and a lateral stop hole 112 are formed on the distal body portion 9 side of the shaft portion 8.

Next, we will explain the direction in which the screw holes 100a are formed, which corresponds to the anteversion angle of the femur, and the direction in which the curved portion 110a of the shaft portion 8 is bent, which corresponds to the lateral curvature of the femur.

First, the direction of the screw hole 100a through which the lag screw 2 is inserted in the intramedullary nail 1a is such that, immediately before the intramedullary nail 1 is inserted into the femur, when the intramedullary nail 1a is viewed from the base end toward the tip end (corresponding to the front view described above), assuming that there is a horizontal plane below the intramedullary nail 1a, the angle between the horizontal plane and the direction of the screw hole 100a is 12° (directed diagonally upward at 12° from the horizontal plane; not shown).

The direction of the curve of the curved portion 110a of the shaft portion 8 is such that, immediately before the intramedullary nail 1a is inserted into the femur, when the intramedullary nail 1a is viewed from the base end toward the tip end (corresponding to the above-mentioned frontal view), the curved portion 110a is curved in such a way that the "vertical line L6 (not shown)" passing through the axis of the starting position of the shaft portion 8 and the "curve corresponding line L7 (not shown)" connecting the axis of the starting position of the shaft portion 8 and the apex of the curve of the curved portion 110a are positioned on the outside of the vertical line L6 as viewed from the femur, and the angle between the vertical line L6 and the curve corresponding line L7 is 5°. This direction of the curve of the curved portion 110a is called a 5° outward curve.

In this way, the intramedullary nail 1a has the above-described direction of the screw hole 100a (12° relative to the horizontal plane) and the direction of curvature of the curved portion 110a of the shaft portion 8 (5° external curvature).

During the procedure, the intramedullary nail 1a is inserted straight into the femur from its tip, and when viewed from the front, the angle of the direction in which the screw hole 100a is formed with respect to the reference line A is 12° without the operator externally rotating the intramedullary nail 1. The angle of the curved corresponding line L7 with respect to the reference line B is 5°, and the direction of the curved portion 110a of the shaft portion 8 is 5° outwardly curved.

In other words, the intramedullary nail 1a can be inserted into the femur and positioned to fit the femur, which has an anterior torsion angle of 12° and a 5° external curvature, without external rotation.

That is, the intramedullary nail 1a can position the tip of the lag screw 2 near the center of the femoral head F1 of a femur with an anteversion angle of 12°. In addition, the position of the tip of the lag screw 2 can be prevented from moving toward the anterior side of the femoral head F1.

In addition, the intramedullary nail 1a can align the direction of the curved portion 110a of the shaft portion 8 with the femur, which has a 5° external curvature. This improves the compatibility of the shaft portion 8 with the femur.

In this way, the intramedullary nail 1a has a unique structure in the direction in which the screw hole 100a is formed (12° from the horizontal plane) and in the direction of the curved portion 110a of the shaft portion 8 (5° lateral curvature), which sufficiently enhances compatibility with femurs that have a certain anteversion angle and lateral curvature shape.

Here, in the second embodiment of the present invention, it is not necessary that the angle between the horizontal plane and the direction in which the screw hole 100a is formed is 12° when viewed from the front and the direction in which the curved portion 110a is curved is 5° outwardly curved in the state immediately before the intramedullary nail 1 is inserted into the femur. For example, the angle between the horizontal plane and the direction in which the screw hole is formed can be set within a range of -2° to 35° when viewed from the front, and the direction of the curved portion can be curved outwardly in the range of 1° to 25° or curved inwardly in the range of 1° to 25°, depending on the anteversion angle or posterior torsion angle and the outward or inward curve shape of the target femur.

As described above, the intramedullary nail of the present invention can prevent problems that occur during the surgical procedure for fractures on the proximal side of the femur, and can be placed in an ideal position within the femur to connect and adequately fix the bone fragments.

The invention made by the inventor has been specifically described above based on the embodiment, but it goes without saying that the invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention.

A Bone connection device 1 Intramedullary nail 10 Main body proximal portion 10a Same diameter portion 10b Reduced diameter portion 11 Shaft portion 110 Curved portion 12 Main body distal portion 120 Opening (of long axis hole) 13 Base end (of intramedullary nail) 14 Tip (of intramedullary nail) 100 Screw hole 101 Pin hole 2 Lag screw 3 Sub-pin 4 Locking screw 5 Locking screw F Femur F1 (femur) head F2 (femur) neck F3 Medial condyle F4 Lateral condyle F5 (femur) shaft F6 Posterior edge of greater trochanter F7 (femur) distal portion F8 (femur) proximal portion F9 Cortical bone (on the anterior side of the femur) S1 Femoral neck axis S2 Femoral condyle axis M Center of medullary cavity M1: Both ends of the center of the medullary cavity M2: The position of the center of the medullary cavity that corresponds to the apex of the lordotic shape L1: The position directly below the lesser trochanter (of the femur) L2: The position directly above the patella (of the femur) L3: Vertical line L4: Curvature corresponding line L5: Line that corresponds to the extension line of the axis of the proximal part of the main body in a side view G: The axis of the starting position of the shaft part

B: Bone set device 1a: Intramedullary nail 7: Proximal body portion 8: Shaft portion 9: Distal body portion 100a: Screw hole 110a: Curved portion

Claims (3)

an intramedullary nail for use in inserting into a proximal portion of a femur when a proximal side of the femur is fractured and in repositioning and fixing each bone fragment, the intramedullary nail comprising: a cylindrical body having a through hole formed therein, constituting one end side of the body, a body proximal portion having a screw hole formed therein for inserting a lag screw that intersects with the through hole and has a tip positioned within the femoral head of the femur; a shaft portion connected to the body proximal portion, constituting an intermediate portion of the body, having an outer circumferential diameter smaller than an outer circumferential diameter of the body proximal portion, and extending toward the other end side of the body with the same diameter; and a body distal portion connected to the shaft portion and constituting the other end side of the body,
The shaft portion has a curved portion that is curved from the front side toward the rear side of the femur when viewed along the medial-lateral direction of the femur,
When the intramedullary nail is inserted into the femur,
In a direction of the shaft portion viewed from the one end side to the other end side, and with a horizontal line passing through a first axis, which is the axis of the same end side of the shaft portion, as a reference, the curved portion is located above the horizontal line, and a shaft vertical line that is a vertical line perpendicular to the horizontal line and passes through the first axis, and a first curve corresponding line that is a line connecting the first axis and the apex of the curve of the curved portion form a predetermined angle, and the horizontal line and a direction in which the lag screw is inserted in the screw hole form a second angle,
The predetermined angle is an angle of 5° inclined in a counterclockwise direction with respect to the shaft vertical line,
The second angle is 12° when the direction in which the lag screw is inserted in the screw hole is inclined toward the front side with respect to the horizontal line. The main body is formed with a total length in the range of 265 mm to 400 mm,
2. The intramedullary nail according to claim 1, wherein the curved portion is formed in the shaft portion, so that when viewed along the medial-lateral direction of the femur, a distance from a third reference line, which is a line corresponding to the position of a second axis, which is the axis of the proximal main body portion, to a center position of the tip of the distal main body portion is 13 mm or more. The curved portion is composed of four vent portions including a first vent portion, a second vent portion, a third vent portion, and a fourth vent portion,
When viewed along the medial-lateral direction of the femur,
The curvature start position of the first vent portion is 120 mm from one end of the main body proximal portion,
The curvature start position of the second vent portion is 150 mm from one end of the main body proximal portion,
The curvature start position of the third vent portion is 175 mm from one end of the main body proximal portion,
The curvature start position of the fourth vent portion is 205 mm from one end of the main body proximal portion,
The radius of curvature in the range between the curvature start position of the first vent portion and the curvature start position of the second vent portion is 457 mm;
The radius of curvature of the range between the curvature start position of the second vent portion and the curvature start position of the third vent portion is 475 mm;
The intramedullary nail according to claim 1 or 2, wherein a radius of curvature in a range between the curvature start position of the third bent portion and the curvature start position of the fourth bent portion is 637 mm.